Rep. Donna F. Edwards (D-Md.) won a boost to her nine-day-old Senate campaign Thursday in the form of an endorsement from Emily’s List, the powerful political action committee that got its start 30 years ago by backing the lawmaker Edwards hopes to succeed.

Edwards, whose congressional district spans Prince George’s County and part of Anne Arundel County, is vying to win the seat long held by Sen. Barbara A. Mikulski (D-Md.), who announced earlier this month that she would retire after 2016.

She was the second candidate to enter what is expected to become a crowded and competitive Democratic primary field, following Rep. Chris Van Hollen, a member of the House Democratic leadership team whose district mostly covers Montgomery County.

Van Hollen addressed the endorsement Thursday in a brief interview outside the Capitol, where, as ranking member of the House Budget Committee, he led a news conference decrying Republican federal budget proposals now under consideration in the House and Senate.

“Look, I have a 100 percent record on pro-woman issues,” he said. “I’m proud to have the endorsement of women leaders from throughout the state of Maryland and look forward to the debate.”

An endorsement from Emily’s List — which backs the candidacies of Democratic women who support abortion rights — usually means a burst of money, especially for television ads, plus assistance in targeting voters interested in electing progressive women.

Stephanie Schriock, the president of Emily’s List, said in a statement that Edwards is a “true progressive champion” who has advocated for after-school nutrition programs, pay equity and protecting women’s access to ­reproductive health care.

She noted that Edwards would be the second African American woman elected to the Senate, and the first in more than two decades.

Since it was founded in 1985, Emily’s List has grown to include more than 3 million members and has raised more than $400 million for its candidates for national, state and local offices. It has helped to elect 110 Democratic women to the U.S. House and 19 to the U.S. Senate, starting with Mikulski.

On the day Mikulski announced her retirement, Schriock described the diminutive senator as a “powerful ally” who was “among the fiercest advocates [for] women and families that Washington has ever seen.”

She said Thursday that Edwards “shares the progressive Maryland values needed to carry on this important legacy.”

Cummings said in an interview Wednesday that he feels that he has more time than some other candidates to consider a bid.

“I don’t feel pressured, and I’m not pressuring myself,” he said.

Likely candidates need to understand the difference between a House district race and one that stretches from Ocean City to beyond Cumberland in the western nook of the state, Cummings said. He is scheduling several trips to different parts of the state and planning to do more speeches and events with Democrats in far-flung counties.

“I need to get a feel for the whole state,” he said. “I’m moving around the state, talking to people.”

Among the other names being floated as possible Democratic contenders include U.S. Labor Secretary Thomas Perez, a former president of the Montgomery County Council and the secretary of the state’s Department of Labor, Licensing and Regulation.

But at a rally in the District on Wednesday night calling for higher wages for the city’s home health-care workers, Perez said he would not be seeking Mikulski’s seat.

“No, I’m not,” he said, when asked if he would be running. “No means no.”